you can use a dehumidifier to remove the moisture from the air (when you have a power source) but without positive ventilation, smells will still build up AND any mold/mildew spores that may get a start, will stay trapped in the boat to multiply at will wherever they land in a crack or crevice where the moisture may be high enough for the spores to live...
a boat without adequate ventilation will always have a smell, and this smell will eventually permeate the upholstery, clothing, woodwork, books and any other porous surface or item. positive ventilation will keep the air changed out and much fresher, and in time the undesirable boat smell from all the porous surfaces will begin to lessen also.